The Defence Cooperation Agreement(DCA) had been signed by the Finnish government in December.

Aimed to strengthen Finland's security and defence capabilities, the agreement comes after the Nordic country joined NATO in April 2023, following Russia's invasion of Ukraine in February 2022.

Finland's relations with neighbouring Russia, with whom it shares a 1,340-kilometre (830-mile) border, have become increasingly tense after Finland joined the alliance last year.

The deal gives the United States access to 15 military bases in Finland and enables the presence and training of US forces, and prepositioning of defence material in Finnish territory.

It also strengthens cooperation between the two countries in crisis situations.

When Sweden adopted its DCA-agreement on June 18, the vote was preceded by a heated debate with critics saying the treaty opened a door to the deployment of nuclear weapons in the country.

While also a controversial topic in Finland, lawmakers ensured that the treaty applies national law to nuclear weapons, whose import and transit is prohibited on Finnish territory.

The defence agreement is based on respect for Finland's sovereignty, legislation and obligations under international law, says both the government and foreign affairs committee which submitted its report on the treaty last week.

The Foreign Affairs Committee's chairperson, MP Kimmo Kiljunen (Social Democratic Party) described the adoption of the DCA-agreement as a "historic moment" at the plenary session on Monday.

"The task of this agreement is just as the task of NATO membership was, to strengthen the security of Finland and the Finnish people," he said.

The US has concluded similar DCA-agreements with 11 other NATO countries, including Finland's Nordic neighbours Sweden, Norway and Denmark.